62 MARCUS M. HARTOG. 
either directly or after preliminary division of the nuclei 
(Cladophora). 
11. In some Apocytial Plants the gametonucleus (whether 
of iso- or oo-gametes, but not of spermatogametes) is the pro- 
duct of the union of several nuclei, either the ordinary vegeta- 
tive nuclei (Dasycladus), or the offspring of the vegetative 
nuclei by antecedent mitotic divisions (Peronospora). In 
both cases the gametes are obligatory. 
12. Hence preliminary nuclear division is not a necessary 
antecedent to the differentiation of obligatory gametes. 
13. Since the nuclei formed in heterogeneous gametogeny 
(§§ 5—7) are all similar, and contain (in every case when the point 
has been worked out) an equal number of chromatic elements, 
we conclude that the difference between an arrested and a 
functional gamete lies in their cytoplasm, not in their nuclei 
(O. Hertwig). 
14. The alleged “processes of excretion” antecedent to 
fertilisation and incidental to gametogeny are neither universal 
nor uniform. Under this head we may group the following 
processes, which I have made to include all cases where part 
of the gamete takes no share in the formation of the zygote. 
(a) Part of the oogamete is utilised in the formation of a 
receptive or transmitting organ for the male; of this cha- 
racter is the trichogyne in Coleochetez and Floridee; 
the beak with its mucified cytoplasm in Oedogoniee (and 
Vaucheria?). 
(6) The formation of non-nucleated epiplasm by isogametes, 
originally referable to a formation of cell-walls, which remains 
in abeyance, in some apocytial plants (Cladophoree and 
Protomyces; found also in similar formation of the asexual 
zOOSpores). 
(c) The cutting off of a wall of cytoplasm around the central 
vacuole of an apocytium or cell (Acetabularia, Botrydium, 
and Ulothrix). 
(d) A similar excretion to (6) of non-nucleated protoplasm 
from the oospores of Saprolegniee, afterwards resumed by 
them; the same process occurs with the asexual zoospores. 
